BOSTON (CBS) – Nearly one year ago, we were shocked by the worst mass shooting in U.S. history. Forty-nine people were killed at the Pulse nightclub in Orlando, Florida. Some Pulse survivors were in Boston Friday, remembering what they lost and calling on authorities to recognize gun violence as a health crisis.

It was Latin night at Pulse one year ago. Omar Mateen opened up with a semiautomatic rifle in the gay nightclub. “I was shot twice in my lower back,” says Norman Casiano, a survivor.

“We can hear the gunshots, we can hear people screaming,” adds Sylvia Serrano who was also in the club. When it was over there were 49 dead and 53 wounded.

Survivors of Pulse nightclub shooting speak at MGH (WBZ-TV)

On Friday, Mass General Hospital commemorated the one-year anniversary of the Pulse massacre, hosting 27 survivors at a conference looking at gun violence as a public health issue.

“It’s very clear that firearms are as responsible for as many deaths as liver disease, 33,000 deaths a year. Twenty children a day in this country end up in emergency rooms because of injuries due to firearm incident,” MGH Dr. Chana Sacks told the conference.

It was the survivor’s stories of loss and perseverance that struck the most powerful chords. “It’s been great having all the support from other survivors, and support from friends,” says Nathan Orozco, who was at the club that night.

Pulse Nightclub in Orlando, Florida (WBZ-TV)

“Unfortunately something like this happened, but it put a lot of us out there, to be the faces of the community, and to be able to implement a change,” adds Casiano.

“In order to make this right, the gun shops need to ask more questions. We need to be thorough about who we’re giving guns to,” says Sylvia Serrano.

The Pulse survivors plan to attend Boston’s Pride parade Saturday, and be home in Orlando for Monday’s one-year anniversary memorial.